Bilayer vesicles or liposomes whose walls comprise phosphatidyl cholines are being studied as drug carriers, offering the attractive properties of promoting passage of the drugs across cell membranes, increasing drug lifetime in the plasma and retarding drug catabolism. Liposomes are, however, thermodynamically and biologically unstable and the rate of leakage of entrapped drugs is high. Consequently, their practical utility may be limited.
More recently, the concept of polymerized vesicles, formed from polymerizable material has been proposed (Regen et al., J. Am. Chem. Soc. 1980, 102, 6638) as a method of achieving enhanced stability.